Salt lakes blamed for mass extinction

The most catastrophic mass extinction in the history of life on earth may not have been caused by meteors and volcanoes but rather by giant salt lakes, according to a report in the Proceedings of the Russian Academy of Sciences.

Toxic chemicals known as halocarbons produced by microbial processes within salt lakes may have triggered the extinction of some 90 per cent of all life on earth, the report claims.

The study compared modern salt lakes' emissions of chemicals including chloroform, trichloroethene and tetrachloroethene with those found during the late Permian age, when giant salt lakes and hyper-saline seas covered large parts of the planet.

The Zechstein Sea alone, which covered an area the size of France, is estimated to have produced about 20 times the amount of chloroform and five times the amount of tetrachloroethene as annual global industry does today.

“Our calculations show that airborne pollutants from giant salt lakes like the Zechstein Sea must have had catastrophic effects at that time," said Dr Ludwig Weissflog, one of the authors.

The natural production of halocarbons within the lake is believed to have aided, if not caused, an irreversible and accelerating process of desertification, causing “90 per cent of sea species, 60 per cent of reptile and amphibian families, 30 per cent of insect varieties, and most terrestrial plants” to die out.

Halocarbons have been banned from commercial use since 1987, but researchers suggest that the chemicals produced by modern salt lakes has a significant impact on global warming and an accelerating effect on desertification.

The report acknowledges existing theories, which propose that volcanic eruptions and a meteor impact may have contributed to the climatic changes, but suggests that large-scale production of halocarbons may be an additional cause.

"The question as to whether the halogenated gases from the giant salt lakes alone were responsible for it or whether it was a combination of various factors with volcanic eruptions, the impact of asteroids, or methane hydrate equally playing their role still remains unanswered," Weissflog said.

The researchers say the findings of their study has implications in today, suggesting that similarities exist between carbon dioxide cycles in the Permian age and those of global warming today.

"Consequently, we assume that the climatic, geo-chemical and microbial conditions in the area of the Zechstein Sea were comparable with those of the present day salt seas that we investigated," Weissflog said.